The present invention relates to an adjustment valve used for fluid transport pipes that require flow regulation. More specifically, it relates to an adjustment valve suitable for use mainly in ultrapure water lines and various chemical solution lines in the semiconductor industry.
One example of a conventional fluid control valve is a micro-fluid valve as shown in FIG. 9 (see, for example, Patent Document 1). The constitution will be explained with reference to FIG. 9. There are provided a diaphragm valve 42 in which an annularly formed valve body 37 that comes in contact with and separates from a valve seat 36 is formed integrally with a needle 39 insertable into an orifice 38 provided at the center of the valve seat 36 with thin films constituting an outer film 40 and inner film 41; operation means for causing the valve body 37 to come in contact with and separate from the valve seat 36; and an adjustment screw 43 for adjusting the position of the needle 39.
Regarding operation, in a state where the valve body 37 is separated from the valve seat 36 by operation means, the needle 39 is inserted into the orifice 38 to a prescribed degree using the adjustment screw 43, thereby regulating the flow of the control fluid to flowing through the orifice 38.
Patent Document 1: Published Japanese Patent No. 2999429 (page 5, FIG. 1)
However, the conventional fluid control valve has the following problems.
(1) The needle position is adjusted using the adjustment screw 43 and thus when a valve is opened just slightly, just a little rotation of the adjustment screw 43 causes a flow to change, making regulation extremely difficult.
(2) The regulation must be performed on-site, thus restricting the uses and installation locations of the fluid control valve.
(3) While it is possible to control flow by regulating the pressure of externally supplied compressed air, as can be seen from the structure, the sliding resistance of a piston 44 has a major effect, lowering both responsiveness and hysteresis. Therefore, the fluid control valve is unsuitable for high-precision flow control.(4) A spring 45 causes an impelling force to operate on the piston 44. In a case where a chemical solution is a fluid, the spring 45 is subject to corrosion caused by the medical solution, resulting in poor operation. In a case where operation means constitutes a solenoid valve, corrosion also causes poor operation.